There is recently a growing demand for electronic components for use in thermoelectric cooling. Many of these components make use of the Peltier effect. However, this requires the use of chlorofluorocarbons which adversely effects the earths atmosphere. These compound are also regulated which impacts the requirements for local cooling or dehumidifying of electronic appliances and others in small-sized cooling devices.
Among the electronic components which are used for thermoelectric cooling, those using Bi-Te singlecrystalline or polycrystalline solidified matter as a thermoelectric semiconductor substance are known. The thermoelectric semiconductor element is manufactered by electric series bonding of an n-type element and a p-type element, and in the Bi-Te compound element, Se is added to the n-type conductive element in order to adjust the characteristics.
The toxicity of Se used as additive to these elements is high, and the Bi-Te composition itself as the main ingredient is expensive. Accordingly, the range of use of the element has been limited.
The performance of a thermoelectric semiconductor device for thermoelectric cooling is expressed as the performance index Z=s.times.s.times..sigma./k(s.sup.2 .sigma./k), with the Seebeck coefficient as s, the electric conductivity as .sigma., and the thermal conductivity as k. The larger the value of Z in the temperature range around the room temperature, the greater the absorption heat per unit power consumption in thermoelectric cooling or the temperature difference from the cooling side.
As the technology relating to the invention, the thermoelectric characteristic of strontium titanate is described beginning at page A44 of Physical Review Vol. 134, 2A (1964). Barium titanatte is described begining at page 358 and after in Physical Review No. 157, 2 (1967).
The idea of using a copper oxide semiconductor for thermoelectric cooling is disclosed begining at page 111 of Materials Science and Engineering Vol. B7 (1990).
In the Japanese Laid-open Patent HEI. 1-231383, barium titanate semiconductor materials are disclosed as the materials suited to application of the Seebeck thermoelectromotive force in a heat sensor.
Aside from these, various semiconductor materials have been studied, but, except for Bi-Te compounds, no practical materials have been known hitherto for use in thermoelectric cooling.